The present exemplary embodiments relate to spacers for aerial cables and to cable retainers for holding the cables relative to the spacers. They find application in conjunction with spacers for power distribution cables, and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiments are also amenable to other like applications including anywhere elongate objects are to be held in a spaced apart relationship.
Overhead utility cables are commonly suspended from a messenger cable typically made of a high strength metal alloy. The messenger cables are strung between spaced apart towers, utility poles, and the like throughout various areas for purposes of supporting utility cables such as power distribution cables into those areas. In typical large scale applications, three phase power is distributed into residential or commercial areas. One example is 15 kv three phase power carried on three separate conductors and distributed into the service area suspended under messenger cables supported on poles or towers in the manner described above.
It is to be appreciated that current carrying conductors should not be permitted to come into contact with each other. Insulation on jacketed conductors can be worn away and, of course, contact between uninsulated conductors would result in a short circuit fault in the grid system. Therefore, typically, the power conductors are carried below the messenger cable by an aerial cable spacer device. A primary function of the spacer is to suspend the power cables from the messenger cable and carry the cables throughout the service area. Another function of the spacer device is to establish and maintain a predefined distance between the power conductors for various reasons such as, for example, to control system characteristics including material reactive impedance characteristics.
One prior art aerial cable retainer device is shown in U.S. Pat. No. 4,020,277 which shows a basic spacer for supporting a set of three electrical conductor cables above the ground. The spacer taught there includes a body member having four concave seats including one downwardly oriented seat adapted to receive a messenger cable and three upwardly oriented seats adapted to receive as many power conductor cables. Each of the concave seats is associated with at least one generally arcuate cable retaining arm for engaging a surface of the conductor cable and messenger cable and holding them in their respective seats. One end of each of the cable retaining means is pivotally connect with the body member and ratchet tooth means in the form of a pawl is provided on the other free end of the cable retaining arm. A set of ratchet tooth means are also provided on the spacer body member outwardly of the concave seats and are generally arranged in the shape of an arc. The teeth of the retainer arms are engageable with the teeth of the body member ratchet tooth means when the retaining arms are rotated about their pivotal supports thereby to hold the conductor cables and messenger cable in their respective concave seats. It has been found at times, however, that the prior art spacers of this type experience a less than desirable force exerted against the cables held in their respective concave seats. In addition, in the prior devices, it was difficult to close the cable retainer with sufficient force exerted on the cable.
U.S. Pat. No. 6,047,930 teaches a cable retaining arm in a spacer for aerial cables of the type described in the '277 patent but includes an additional fulcrum point carried on the arm. The fulcrum point engages and exerts a force on the cable as the cable retaining arm bends to a closed position. However, the cable retaining arm taught in the '930 patent is difficult to manufacture, adds cost to the device due to the additional materials needed to form the fulcrum point, and presents potential inherent stress and fracture areas adjacent either side of the fulcrum point section as the cable retaining arm is biased into position across the respective cable.
U.S. Pat. No. 6,170,783 proposes a further modification to a cable retaining arm in a spacer for aerial cables of the type described in the '277 patent. In the '783 patent, a resilient pad is secured to either or both of the cable seat on the spacer main body member as well as on the cable retaining arm. When a cable is located in the cable seat and the cable retaining arm is closed upon the cable, the resilient pad is compressed and is said to act like a spring to maintain a force on the cable. The resilient pad concept applied to the cable retaining arms of a spacer for aerial cables as proposed in the '783 patent adds further complexity and cost to the product and, it is believed, invites mechanical failure in the arm in the high-stress regions adjacent either side of the resilient pad.
Lastly, U.S. Pat. No. 6,303,856 proposes various means for providing an anti-dislodging cable retainer in a cable spacer device of the type taught in the '277 patent. In the '856 patent, either a slot or a groove are formed on respective opposite ones of the cable retaining arm and the cable seat on the body member for establishing a mechanical interlock between a ratchet tooth carried on the cable retaining arm and a plurality of spaced apart ratchet teeth formed on the spacer body member. The abutment surfaces described in the '856 patent introduce manufacturing burdens and complexities in the final product.
Thus, there is a need in the art for improved aerial cable spacers which are easy to manufacture and use and for cable retaining arms with enhanced clamping and cable holding capabilities for connecting associated cables with cable spacer bodies of aerial cable spacers.